Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 131548 AAA AFDLWX AREA FORECAST DISCUSSION...UPDATED NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC 1048 AM EST SAT DEC 13 2014 .SYNOPSIS... HIGH PRESSURE WILL BUILD OVER THE REGION THROUGH MONDAY. A COLD FRONT WILL PASS THROUGH THE AREA TUESDAY AND HIGH PRESSURE WILL RETURN FOR THE MIDDLE AND LATTER PORTION OF NEXT WEEK. && .UPDATE... ISSUED NEW AFD TO REMOVE FREEZING RAIN ADVISORY FROM WATCHES/WARNINGS/ADVISORIES SECTION BELOW. .NEAR TERM /THROUGH TONIGHT/... HIGH PRESSURE TO THE WEST WILL CONTINUE TO PROVIDE NORTHWEST FLOW ACROSS THE MIDDLE ATLANTIC REGION TODAY. MOST AREAS OF THE CWFA WILL EXPERIENCE DOWNSLOPING CONDITIONS WITH SOME HIGH LEVEL CLOUDS AND NEAR SEASONABLE HIGH TEMPERATURES. DECENT MIXING WILL ALLOW FOR BREEZY NW WINDS WITH GUSTS OF 15-25 MPH EXPECTED THROUGH LATE AFTERNOON. NW UPSLOPE FLOW WILL PERSIST OVER THE POTOMAC HIGHLANDS WITH SOME LOW LEVEL MOISTURE AND ADDED CLOUD COVER EXPECTED. BAYARD OBSERVER REPORTED MOSTLY CLOUDY WITH A FEW PEAKS OF SUNSHINE. CONDITIONS ARE TRENDING AWAY FROM FREEZING DRIZZLE/FOG THREAT OVER THE WESTERN FIVE. WILL GO AHEAD AND LET THE FREEZING RAIN ADVISORY EXPIRE. SEASONABLY CHILLY CONDITIONS ARE EXPECTED ACROSS THE REGION TONIGHT AND IT WILL TURN OUT DRY FOR MOST AREAS. HOWEVER...MOISTURE IS EXPECTED TO RIDE OVER THE MOUNTAINS AND WILL BE DEEPER THAN THIS MORNING. THEREFORE...CONFIDENCE IS HIGHER IN MORE FREEZING DRIZZLE AND PERHAPS EVEN LIGHT FREEZING RAIN ALONG AND WEST OF THE ALLEGHENY FRONT. A FREEZING RAIN ADVISORY MAY BE NEEDED FOR THESE AREAS. && .SHORT TERM /SUNDAY THROUGH MONDAY/... HIGH PRESSURE WILL REMAIN JUST TO OUR WEST THROUGH SUNDAY BEFORE BUILDING OVERHEAD SUNDAY NIGHT INTO MONDAY. MOST AREAS WILL TURN OUT DRY AND TEMPS WILL ACTUALLY BE A BIT ABOVE NORMAL DUE TO AN UPPER-LEVEL RIDGE BUILDING OVERHEAD. HOWEVER...MORE CLOUDS ALONG WITH FREEZING DRIZZLE/LIGHT FREEZING RAIN IS EXPECTED ALONG AND WEST OF THE ALLEGHENY FRONT SUNDAY MORNING. HOWEVER...TEMPS SHOULD RISE ABOVE FREEZING ACROSS THESE AREAS SUNDAY AFTERNOON CAUSING PRECIP TO CHANGE TO JUST PLAIN DRIZZLE/LIGHT RAIN. THE DRIZZLE WILL CONTINUE ALONG AND WEST OF THE ALLEGHENY FRONT SUNDAY NIGHT...BUT OTHER LOCATIONS WILL BE DRY. DRY CONDITIONS AND SUNSHINE IS EXPECTED ACROSS MOST AREAS MONDAY AS HIGH PRESSURE ROTATES THROUGH. IT WILL TURN OUT TO BE A MILD AFTERNOON WITH HIGHS NEAR 50 FOR WASHINGTON AND BALTIMORE. HOWEVER...LOW CLOUDS MAY HANG AROUND FOR LOCATIONS NEAR THE ALLEGHENY FRONT. && .LONG TERM /MONDAY NIGHT THROUGH FRIDAY/... ELONGATED AREA OF HIGH PRESSURE COVERS THE EAST COAST BY MONDAY NIGHT AS THE SFC HIGH BUILDS EAST. ALOFT...RIDGE AXIS PUSHES THROUGH LATE IN THE DAY MONDAY...WITH MID LVL TROUGH SWINGING THROUGH THE MID WEST. BACK TO THE SFC...LOW PRESSURE LIFTS NORTH INTO THE MIDWEST MONDAY NIGHT. AS THE HIGH NUDGES EAST...RETURN FLOW WILL START TO MOISTEN THE LOWER LVLS. HOWEVER...GENERAL CONSENSUS AMONGST THE 00Z MODEL SUITE SUGGESTS ANY PCPN FORMATION HOLDS OFF TILL AFTR 06Z TUES WITH BUFKIT SOUNDINGS INDICATING THE VERTICAL COLUMN NOT BECOMING SATURATED ENOUGH TILL CLOSER TO 12Z FOR FAR WESTERN REACHES OF THE CWA...AND EVEN LATER FOR THE EASTERN AREAS. AS SUCH...HAVE DRY FORECAST FOR THE FIRST HALF OF MONDAY NIGHT...WITH CHC POPS THEN BLUE RIDGE AND WEST SECOND HALF OF THE NIGHT. FOR PCPN TYPE...GOOD WAA WITH THE SOUTHERLY FLOW MONDAY SHOULD KEEP TEMPS WARM ENOUGH EVERYWHERE EXCEPT ALLEGHENY FRONT FOR RAIN SHOWERS. NO SNOW ACCUM IS EXPECTED OVERNIGHT. FOR TUESDAY...SFC LOW CONTINUES TO LIFT NORTH INTO SOUTHEASTERN CANADA...DRAGGING ITS ASSOCIATED COLD FRONT THROUGH THE REGION SOMETIME LATE TUESDAY AFTN-EVENING. BROAD UPPER LVL TROUGH PIVOTS OVER THE MIDWEST...SENDING MULTIPLE SHORTWAVES/ASSOCIATED VORT MAXES THROUGH. COMBINATION OF LIFT AT THE SFC WITH THE FRONT AND FORCING ALOFT WITH THE WAVES SHOULD RESULT IN AT LEAST SCT SHOWERS WITH THE BEST CHC OF ANY PCPN OCCURRING RIGHT ALONG THE FRONT LATE TUES. TEMPS IN THE 40S/50S WILL KEEP RAIN SHOWERS DURING THE DAY. THE PCPN TAPERS OFF QUICKLY OVER EASTERN AREAS AS THE TROUGH ALOFT WEAKENS AND BECOMES ALMOST ZONAL FLOW...THUS LOSING THE MOMENTUM WITH THE FRONT. HOWEVER...HIGH PRESSURE BUILDING IN THE WAKE OF THE FRONT AT THE SFC BRINGS WINDS TO A W-NW FLOW SO MAINTAINING POPS TO ACCOUNT FOR UPSLOPE SNOW SHOWERS WEST OF THE ALLEGHENY FRONT. SOME DISCREPANCIES IN THE MODEL SOLUTIONS FOR THE LATTER HALF OF THE WEEK. AGREEMENT BETWEEN THE GLOBAL MODELS IN HIGH PRESSURE BUILDING IN. THE GFS HOWEVER IS QUICKER TO WEAKER AND RETREAT THE HIGH AS DEVELOPING LOW PRESSURE IN THE SOUTH CENTRAL US TAKES MORE OF AN INSIDE RUNNER PATH...WHILE THE ECMWF IS SLIGHTLY SLOWER AND TRACKS THE LOW MORE AS A COASTAL LOW PATH. AS SUCH...WITH LOW CONFIDENCE OF HOW THIS LOW WILL EVOLVE...SIDED WITH A DRY FORECAST FRIDAY AND SLIGHT CHC POPS FRIDAY NIGHT. && .AVIATION /16Z SATURDAY THROUGH WEDNESDAY/... A NORTHWEST FLOW WILL CONTINUE FOR TODAY WITH GUSTS AROUND 15 TO 20 KNOTS THROUGH THIS AFTERNOON. VFR CONDITIONS ARE EXPECTED ACROSS MOST OF THE TERMINALS. HOWEVER...THERE WILL BE SOME MOISTURE MOVING IN FROM THE NORTHWEST AND THIS MAY CAUSE A STRATOCU DECK NEAR OR JUST BELOW 3KFT...ESPECIALLY ACROSS KBWI AND KMTN. A STRATOCU DECK MAY AFFECT THE TERMINALS TONIGHT WITH MVFR CONDITIONS...BUT CONFIDENCE IS LOW AT THIS TIME. THE NORTHWEST FLOW WILL CONTINUE THROUGH SUNDAY WITH GUSTS AROUND 15 TO 20 KNOTS EXPECTED LATER SUNDAY MORNING AND AFTERNOON. HIGH PRESSURE WILL BUILD OVERHEAD MONDAY. WINDS WILL BE LIGHTER AND VFR CONDITIONS ARE EXPECTED. GENERALLY VFR CONDITIONS MONDAY NIGHT...WITH DIMINISHING CONDITIONS AS PCPN MOVES IN. SUB-VFR CONDITIONS LIKELY WITH ANY PCPN TUES. VFR WED WITH WNW WINDS GUSTING 20-25 KTS. VFR CONDITIONS LAST THROUGH THE END OF THE WEEK WITH DIMINISHING WINDS AS HIGH PRESSURE BUILDS IN. && .MARINE... HIGH PRESSURE WILL BUILD TOWARD THE WATERS THROUGH THE WEEKEND. A SMALL CRAFT ADVISORY IS IN EFFECT FOR PORTIONS OF THE WATERS DURING THIS TIME. WINDS WILL DIMINISH SUNDAY NIGHT AND MONDAY AS HIGH PRESSURE BUILDS OVERHEAD. SUB-SCA CONDITIONS INITIALLY MONDAY NIGHT...THOUGH GUSTS INCREASING BY TUESDAY MORNING AHEAD OF AN APPROACHING COLD FRONT. GUSTS TO 18 KTS PSBL DURING THE DAY TUES...WITH HIGHER CONFIDENCE OF OCCURRING TUES EVENING. A BRIEF LULL TUES WITH THE PASSAGE OF THE FRONT...THEN GUSTS INCREASE AGAIN INTO THE 20S AS WINDS SHIFT TO THE WEST BEHIND THE FRONT. SCA CONDITIONS THEN EXPECTED THROUGH WED AND POSSIBLY THROUGH WED NIGHT. && .LWX WATCHES/WARNINGS/ADVISORIES... DC...NONE. MD...NONE. VA...NONE. WV...NONE. MARINE...SMALL CRAFT ADVISORY UNTIL 6 PM EST SUNDAY FOR ANZ531>534-537- 539>541-543. SMALL CRAFT ADVISORY UNTIL 3 PM EST THIS AFTERNOON FOR ANZ530- 535-536-538-542. SMALL CRAFT ADVISORY FROM 9 AM TO 6 PM EST SUNDAY FOR ANZ530- 535-536-538-542. && $$ SYNOPSIS...BJL UPDATE...KRW NEAR TERM...KRW SHORT TERM...BJL LONG TERM...SEARS AVIATION...SEARS/KRW MARINE...SEARS/KRW

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